1. Field of the Invention
The present invention relates generally to an acoustic wave therapy apparatus for treating cancerous cells or calculi in a human body, using shock waves produced by acoustic waves or continuous acoustic waves, and more particularly to an ultrasonic shock wave lithotrity apparatus and an ultrasonic continuous wave hyperthermic therapy apparatus.
2. Description of the Related Art
Conventional acoustic wave treatment apparatuses include an ultrasonic shock wave lithotrity apparatus for breaking calculi, etc. in a human body, using shock waves due to focusing ultrasonic energy, and an ultrasonic continuous wave hyperthermic therapy apparatus for treating a tumor by heating it up to a lethal temperature, using continuous focusing ultrasonic energy.
This type of acoustic wave treatment apparatus generally has an irradiation device for generating ultrasonic waves. The irradiation device has a concave surface for focusing the generated ultrasonic waves. The acoustic wave generator is arranged to face a subject, with a bag interposed therebetween. An ultrasonic imaging probe is arranged within the bag, for positioning the irradiation device and for obtaining tomograms of the subject for confirming the result of treatment.
If a large-diameter acoustic wave generator is employed in this apparatus and generated waves are focused onto a region-of-interest (ROI), a maximum treatment effect is attained with a small treatment energy. In this case, however, if the focus of waves departs from the ROI, a normal tissue is damaged. It is thus important to precisely focus the waves onto the ROI.
FIG. 1 is a cross-sectional view for schematically showing a structure of an applicator serving as an important part of an acoustic wave therapy apparatus having this type of imaging means. In FIG. 1, ultrasonic transducers 2 serving as an irradiation device are secured to a holder 4 having a concave surface. The ultrasonic transducers 2 are arranged symmetrical in respect of a probe rod 16 (described later) so that the focal points of the transducers 2 may be positioned at a region-of-interest (ROI) 6.
The acoustic wave therapy apparatus has a bag 10 containing water 8 which is put in close contact with a patient 12. The probe rod 16 having an ultrasonic probe 14 is arranged at the center of the holder 4. The ultrasonic probe 14 effects positioning for treatment by means of an image display process, thereby confirming if the ROI 6 has been treated appropriately In FIG. 1, a dot-and-dash line indicates a region 18 where ultrasonic waves for treatment are radiated, and a two-dot-and-dash line indicates a region 20 (a tomogram display region) where ultrasonic waves for ultrasonic imaging are radiated.
When an acoustic wave therapy is performed by this apparatus, a tomogram is formed on the basis of a reflected wave signal received by the ultrasonic probe 14. Observing the tomograms, an operator moves the apparatus so that the focal points of the ultrasonic transducers 2 may coincide with the location of the ROI 6, or positions the apparatus by supplying water 8 into and letting water 8 out of the bag 10. When the focal points of the transducers 2 have coincided with the location of the ROI 6, the transducers 2 are driven, e.g. by intense pulse waves to radiate intense ultrasonic waves onto the ROI 6, thereby subjecting the ROI 6 to, e.g. lithotrity.
The positioning of the focal points of the transducers 2 relative to the ROI 6 will now be described. The size of the bag 10 is adjusted by supplying the water 8 thereinto and letting out the water 8 therefrom. Thus, the focal points of the transducers 2 can be freely positioned relative to the ROI 6. The water 8 is supplied into and discharged from the bag 10 through a pipe (not shown) arranged above the holder 4 or the bag 10.
In the above apparatus, however, the water 8 in the bag 10 cannot completely be discharged from the bag 10 since the water 8 is discharged through the pipe arranged above the holder 4 or the bag 10. As a result, the water 8 would remain on the bottom of the bag 10, and the ultrasonic probe 14 is always put in the water 8. This leads to deterioration of characteristics of the ultrasonic probe 14.